The long-term objectives of this research proposal are to study the biology of T lymphocytes that are reactive with Histoplasma capsulatum. To facilitate these studies, murine T cell lines that recognize histoplasmin have been generated and more recently, these lines have been cloned. The surface phenotype of the cloned T cells will be determined by flow microfluorometry. The capacity of these T cells to proliferate in response to heterologous fungal antigens will be measured. The in vitro and in vivo immunoregulatory function of T cell clones will be determined as well as their ability to produce immunoregulatory factors. In addition, partial characterization of the component of histoplasmin that stimulates proliferation of cloned T cells will be examined. Attempts will be made to generate clonotypic antibodies to the cloned T cells. Both an antisera and a monoclonal antibody will be produced. Clonotypic antibodies will be tested for their capacity to modulate the proliferative response of cloned T cells to histoplasmin. Finally, clonotypic antibodies will be used to characterize partially the surface receptor on cloned T cells that recognizes Histoplasma capsulatum.